WASHINGTON — Students of Osama bin Laden at the CIA got more homework Monday.
Another tape thought to be from the terrorist leader, this one urging a boycott of Iraqi elections, was the sixth audio or videotape from Bin Laden since September. It was more grist for a battery of CIA analysts who have been scouring the recordings for fresh clues about the Al Qaeda mastermind.
Much of the effort has focused on studying the statements for new insights into Bin Laden's intentions. But U.S. intelligence officials say that with each new tape there is a parallel and equally energetic effort to examine every aspect of the recording for inadvertent leads on matters ranging from Bin Laden's whereabouts to his health.
The effort has been growing in intensity, fueled by swelling budgets and payrolls since the Sept. 11 attacks on the United States. And there have been some small successes, said current and former intelligence officials familiar with the efforts. But until Bin Laden is killed or captured, the true payoff remains elusive.
The CIA has tapped geologists to examine rock formations seen in the background of Bin Laden's tapes, and has turned to botanists for help in identifying trees or shrubs, all in an effort to detect any unique stones or flora that could yield clues to his location.
The agency has enlarged images of the maps used as backdrops in some videotapes to scan for telltale markings. Analysts have argued about whether Bin Laden wore a certain knife to send a coded message to operatives. And CIA psychiatrists and doctors have studied Bin Laden's appearance and mannerisms for clues about possible psychological irregularities and the extent of his reported ailments.
The effort is not confined to U.S. intelligence. German authorities thought they heard a bird chirping in one of Bin Laden's audiotapes this year, and brought in ornithologists to identify the species -- and its habitat -- according to reports in the German media. They did identify the bird, a source said, but the clue hasn't helped find Bin Laden.
Even those involved in the efforts acknowledge that they can be taken to extreme, if not ridiculous, lengths. But, they say, failure to obsess over such details would raise the risk of overlooking important clues.
"It's a good example of people putting too much emphasis on superficial aspects of the tape, when what Bin Laden says is typically much more important than what he wears," said Michael Scheuer, who left the CIA recently after serving as head of the unit tracking Bin Laden.
But, Scheuer acknowledged, "There's a tremendous desire to make sure we exhaust every lead."
Some see parallels with the Cold War, when no aspect of a Soviet leader's public appearances was too obscure for analysts seeking clues to Moscow's inner workings.
The examinations of Bin Laden's tapes "have taken on their own sort of Kremlinology," said Roger W. Cressey, a former counter-terrorism official in the Clinton and Bush administrations. "Instead of trying to figure out who's standing next to [former Soviet leader Leonid] Brezhnev and whether he's in the ascendancy, now we're trying to discern the meanings of these tapes."
Current and former CIA officials say the useful information gleaned from the tapes includes clues on Bin Laden's approximate location in the Afghan-Pakistani border region. Some tapes have also been useful in corroborating reports from other sources on Bin Laden's health.
But in some ways, the enterprise has been more remarkable for its optimism than for its effectiveness.
Bin Laden and his senior aides have given the CIA a significant volume of recorded material to review. The Al Qaeda leader has been releasing tapes since the late 1970s, and since Sept. 11, 2001, has made at least 18 audio or video messages, U.S. officials said. Counting appearances by his top deputy, Ayman Zawahiri, the total is 30, or about one new tape from Al Qaeda's top leaders every six weeks.
Experts say Al Qaeda has long recognized the propaganda value of the tapes, and even before Sept. 11 was using professional production techniques. Many tapes bear the marking of "Al Sahab," which is thought to be the name of Al Qaeda's media committee.
Bin Laden's recent messages "have had to do less with specific attacks and more with showing the organization is still alive," said a CIA official, who spoke on condition of anonymity.
The latest tape, broadcast Monday on the Al Jazeera satellite TV channel, publicly praised Abu Musab Zarqawi, the Jordanian-born militant said to be a leading figure in the insurgency in Iraq, and urged Iraqis not to vote in the Jan. 30 elections.
"Anyone who takes part in this election consciously and willingly is an infidel," said the speaker on the tape.